Wire electric discharge machining device

ABSTRACT

A wire-electrical discharge machine infuses a processing liquid in a gap between a wire and a workpiece and processes the workpiece using predetermined processing parameters. The machine includes processing parameter storage means that stores processing parameters, means that stores a relationship between the nozzle heights and the amount of processing energy, processing energy determining means that determines the amount of processing energy, for example, during rough processing based on such relationship, and processing parameter changing means that changes the processing parameters based on the amount of processing energy. The workpiece is processed using the changed processing parameters. According to this construction, wire breakage can be prevented and the accuracy of the processed surface can be improved.

TECHNICAL FIELD

[0001] The present invention relates to a wire-electrical dischargemachine.

BACKGROUND ART

[0002] Generally, wire-electrical discharge machining involves three toseven processing steps that include rough processing, intermediateprocessing, semi-finishing, and finishing, wherein the processing isperformed while reducing the amount of energy. The purpose of this is toreduce the processing time by gradually reducing the surface roughness,as well as to increase the precision of the straightness of theprocessed surface. Furthermore, it is known that during wire-electricaldischarge machining, due to wire vibration caused by dischargerepulsion, electrostatic force or the like, the part of the wire facingthe center part of a workpiece may become dented, or may swell into aso-called ‘drum shape’. Furthermore, the processing conditions arecompletely different between the first processing step (roughprocessing) and the subsequent processing steps (intermediateprocessing, semi-finishing, and finishing). In the first processingstep, because processing is performed on a virgin workpiece, there is adanger that processing debris will not be adequately eliminated from theworkpiece, and that the wire may break due to the presence of thedebris.

[0003]FIG. 19 depicts a conventional wire-electrical discharge machineas disclosed in Japanese Patent Publication No. 7-16825, which includesinput means 120 for inputting the plate thickness of a workpiece, theheights of nozzles and the like, processing parameter storage means 121that stores the charging voltage, the ON period, the OFF period and thelike, liquid pressure calculation means 122 that calculates the nozzleliquid pressure from the nozzle heights and other parameters, andprocessing parameter changing means 123 that changes the processingparameters based on the calculated nozzle liquid pressure, and seeks thenozzle liquid pressure, i.e., the processing liquid pressure, based onthe nozzle heights, and changes the processing parameters based on theprocessing liquid pressure. In the first processing step, however, ifthe nozzles are sufficiently distanced from the workpiece, wire breakageis caused not by the liquid pressure during processing but by the wirelength. It is therefore difficult to reliably prevent breakage of thewire using the method in which the processing parameters are calculatedfrom the processing liquid pressure. In actual experiments, it has beendetermined that where the distance between the upper nozzle and theworkpiece was 2 mm, (with a plate thickness of 20 mm and a wire having adiameter of 0.25 mm), the processing liquid pressure varies, but wherethe distance is longer than it, there is no change in processing liquidpressure. However, the problem arises that when the wire is long, itwarps easily, and it is difficult to perform control when ashort-circuit occurs, resulting in an increased likelihood of wirebreakage. The present invention has been developed to solve theabove-described problems, and an object thereof is to provide awire-electrical discharge machine wherein the wire is not likely tobreak even where the nozzles are located at a distance from theworkpiece. Furthermore, while the surface precision of the processedsurface and processing accuracy are important in wire-electricaldischarge machining, such processing accuracy is not taken into accountin the conventional art.

DISCLOSURE OF THE INVENTION

[0004] The wire-electrical discharge machine according to a first aspectof the present invention includes processing parameter storage meansthat stores processing parameters, means that stores a relationshipbetween a nozzle height and an amount of processing energy, processingenergy determining means that determines the amount of processing energyduring rough processing based on such relationship, and processingparameter changing means that changes the processing parameters based onthe amount of processing energy. The workpiece is processed using thechanged processing parameters. According to this construction, becausethe amount of processing energy is determined based on the wire nozzleheight, the wire is not likely to break even where the nozzle is locatedat a far distance.

[0005] The wire-electrical discharge machine according to a secondaspect of the present invention includes processing parameter storagemeans that stores standard processing parameters, means that stores arelationship between a nozzle height and an amount of liquid flow, meansthat determines the amount of liquid flow during rough processing basedon such relationship, and liquid flow rate changing means that changes aliquid flow rate parameter among the processing parameters. Theworkpiece is processed using the changed processing parameters.According to this construction, because the processing liquid flow rateis determined in accordance with the nozzle height, the wire is notlikely to break.

[0006] The wire-electrical discharge machine according to a third aspectof the present invention includes processing parameter storage meansthat stores standard processing parameters, means that stores arelationship between a nozzle height and an amount of wire tilt, tiltcorrection value determining means that determines the amount of wiretilt during processing based on such relationship, and tilt correctionvalue changing means that changes a tilt correction value parameteramong the processing parameters. The workpiece is processed using thechanged processing parameters. According to this construction, the tiltcaused by warping of the wire is corrected, thereby increasing surfaceprecision and processing accuracy.

[0007] The wire-electrical discharge machine according to a fourthaspect of the present invention includes processing parameter storagemeans that stores standard processing parameters, means that stores arelationship between a nozzle height and an amount of wire shift, shiftamount correction value determining means that determines the amount ofwire shift during processing based on such relationship, and shiftamount changing means that changes a wire shift amount parameter amongthe processing parameters. The workpiece is processed using the changedprocessing parameters. According to this construction, the amount ofwire shift takes into account the degree of warping of the wire, therebyimproving surface precision.

[0008] The wire-electrical discharge machine according to a fifth aspectof the present invention includes processing parameter storage meansthat stores standard processing parameters, nozzle distance detectionmeans that detects a processing state in a first processing step anddetects a nozzle distance from the detected processing state, andprocessing parameter determining means that determines the processingparameters for subsequent processing steps based on the detected nozzledistance. The workpiece is processed using the determined processingparameters. According to this construction, because the correct nozzleheight can be automatically detected and correction can be performed inaccordance with such nozzle height, surface precision can be improved.

[0009] In the wire-electrical discharge machine according to the fifthaspect of the present invention, the wire-electrical discharge machineaccording to a sixth aspect of the present invention detects theprocessing speed as the processing state. According to thisconstruction, surface precision is improved.

[0010] In the wire-electrical discharge machine according to the fifthaspect of the present invention, the wire-electrical discharge machineaccording to a seventh aspect of the present invention further includesmeans for displaying a state of separation of a wire nozzle in agraphical fashion. According to this construction, errors during settingor inputting can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram showing the construction of Embodiment 1of the present invention;

[0012]FIG. 2 is a flow chart showing the operation of Embodiment 1 ofthe present invention;

[0013]FIG. 3 is an explanatory drawing showing the construction of aprocessing energy database in connection with Embodiment 1 of thepresent invention;

[0014]FIG. 4 is a block diagram showing the construction of Embodiment 2of the present invention;

[0015]FIG. 5 is a flow chart showing the operation of Embodiment 2 ofthe present invention;

[0016]FIG. 6 is an explanatory drawing showing the construction of aliquid flow rate database in connection with Embodiment 2 of the presentinvention;

[0017]FIG. 7 is a block diagram showing the construction of Embodiment 3of the present invention;

[0018]FIG. 8 is a flow chart showing the operation of Embodiment 3 ofthe present invention;

[0019]FIG. 9 is an explanatory drawing showing the construction of atilt correction value database in connection with Embodiment 3 of thepresent invention;

[0020]FIG. 10 is diagrams showing the state of a wire in connection withEmbodiment 3 of the present invention;

[0021]FIG. 11 is a block diagram showing the construction of Embodiment4 of the present invention;

[0022]FIG. 12 is a flow chart showing the operation of Embodiment 4 ofthe present invention;

[0023]FIG. 13 is an explanatory drawing showing the construction of ashift amount correction value database in connection with Embodiment 4of the present invention;

[0024]FIG. 14 is a diagram showing the state of the wire in connectionwith Embodiment 4 of the present invention;

[0025]FIG. 15 is a block diagram showing the construction of Embodiment5 of the present invention;

[0026]FIG. 16 is a flow chart showing the operation of Embodiment 5 ofthe present invention;

[0027]FIG. 17 is an explanatory drawing showing the construction of aprocessing speed database in connection with Embodiment 5 of the presentinvention;

[0028]FIG. 18 is diagrams showing in a graphical fashion the wire nozzleseparation state in connection with Embodiments 1-4 of the presentinvention; and

[0029]FIG. 19 is a block diagram showing the construction of aconventional wire-electrical discharge machine.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] Embodiments of the present invention will be described below withreference to the drawings. In the drawings, identical or equivalentcomponents are assigned the same symbols, and explanation thereof willbe omitted.

[0031] Embodiment 1

[0032]FIG. 1 is a block diagram of Embodiment 1 of the presentinvention. In the drawing, 1 is input means that is normally a keyboard,and 2 is processing energy determining means. 3 is a processing energydatabase, and as shown in FIG. 3, the processing energy amounts withwhich the wire will not break are stored corresponding to variouscombinations of the plate thickness of the workpiece, the upper nozzleheight and the lower nozzle height, as percentages of the normalstandard processing parameters described above. Regarding the nozzleheights, the upper nozzle 70 is separated from the workpiece 72 as shownin part (A) of FIG. 10, for example. This percentage data exists onlywith regard to the first processing step. The processing energy isdetermined by the processing energy determining means 2 based on thedata regarding the plate thickness, the upper nozzle height and thelower nozzle height read out from the processing energy database 3. Theprocessing energy data determined by the processing energy determiningmeans 2 is sent to the processing parameter changing means 4. 5 isprocessing parameter storage means that stores the charging voltage, theON period, the OFF period, the shift amount and the like as standardprocessing parameters (n steps: n≧1) during nozzle contact (i.e., whenthe nozzles are in contact with the workpiece). The processing parameterchanging means 4 changes the processing parameters sent from theprocessing parameter storage means based on the processing energy datadetermined by the processing energy determining means 2, outputs it to acontroller 7, or displays the processing parameters on a screen (notshown) of an output/display means 6. Here, regarding the nozzle heights,the nozzle 70 is separated from the workpiece 72 as shown in part (A) ofFIG. 10, for example.

[0033]FIG. 2 is a flow chart showing the operation of Embodiment 1 ofthe present invention.

[0034] The first operation will now be explained with reference to FIG.2. The material quality, plate thickness, wire diameter, upper nozzleheight, lower nozzle height and the like are input to the processingenergy determining means 2 via the input means 1 (ST 1-1). The standardprocessing parameters determined based on the material quality, platethickness, wire diameter and the like where the nozzles are in contactwith the workpiece are stored beforehand in the processing parameterstorage means 3, and these standard processing parameters are sent tothe processing parameter changing means 4 (ST 1-2). Based on thematerial quality, plate thickness, wire diameter, upper nozzle height,lower nozzle height and the like input by the input means 1, theprocessing energy determining means 2 determines the amount ofprocessing energy from the table stored in the processing energydatabase 3 and shown in FIG. 3 (ST 2-3). In FIG. 3, where the platethickness is ‘10’, the upper nozzle separation amount is ‘20’ and thelower nozzle separation amount is ‘0’, for example, the processingenergy amount is ‘0.5’ according to No. 2 in FIG. 3, and the processingenergy amount is determined as 50% of the standard first-step amount bythe processing energy determining means 2. The ‘0.5’ information is sentfrom the processing energy determining means 2 to the processingparameter changing means 4. The processing parameter changing means 4reduces the processing energy amount by 50% by increasing the OFFperiod. The processing parameter changing means 4 changes the standardfirst-step processing parameters based on the processing energy amount(ST 2-4). The changed first-step processing parameters are sent to thecontroller 7 together with the unchanged processing parameters for thesecond and subsequent processing steps, and are displayed on the screen(not shown) of the output/display means 6 (ST 1-5). The controller 7performs first-step processing of the workpiece in accordance with theprocessing parameters. During the second and subsequent processingsteps, because there is no need to reduce the processing energy levelsince the wire will not break, processing takes place without a changein the processing parameters. According to this Embodiment 1, becausethe energy amount is controlled in accordance with the nozzle separationamounts, wire breakage can be prevented.

[0035] In Embodiment 1, the processing energy amount is determined basedon the data stored in the processing energy database, but it is alsoacceptable if it is derived through an approximate expression for anenergy amount sought from the nozzle heights and the plate thickness.

[0036] The method in which the processing energy amount is reduced by50% has been described as a method in which the OFF period is increased,but various other methods may also be used, such as a method in whichthe ON period is decreased or the servomotor voltage is increased.

[0037] Where the processing energy amount corresponding to the wirenozzle separation amounts is not known, a processing energy amount suchas ‘0.4’ may be input directly.

[0038] While standard processing parameters have been described as beingstored beforehand in the processing parameter storage means 5, it isacceptable if the standard processing parameters are determined bydifferent means, such as through user input.

[0039] While the method of expression of the energy amount has beendescribed as a percentage of the standard processing parameters forfirst-step processing, it may also take the form of a value calculateddirectly as the energy amount within a certain period of time based onthe current waveform information such as the ON period, the OFF periodor the like. This energy amount expresses the actual energy amountitself. On the other hand, the energy amounts shown in FIG. 3 aredifferent in that they are expressed as percentages of the standardprocessing parameters, as described above.

[0040] Embodiment 2

[0041]FIG. 4 is a block diagram of Embodiment 2 of the presentinvention, and FIG. 5 is a flow chart showing the operation thereof. InFIG. 4, 1 is the same input means used in Embodiment 1, and a keyboardis normally used therefor. 30 is liquid flow rate determining meanspertaining to the processing liquid flow rate (hereinafter ‘liquid flowrate’), and 31 is a liquid flow rate database. As shown in FIG. 6,liquid flow rates that will not break the wire are stored in this liquidflow rate database 31 as percentages of the standard processingparameters corresponding to various combinations of workpiece platethickness, upper nozzle height and lower nozzle height. This percentagedata pertains to processing for the first processing step only. Theliquid flow rate determining means 30 determines the liquid flow ratebased on the data read out from the liquid flow rate database 31. Theliquid flow rate data determined by the liquid flow rate determiningmeans 30 is sent to liquid flow rate changing means 32. 5 is the sameprocessing parameter storage means used in Embodiment 1, and this meansstores such parameters as the charging voltage, the ON period, the OFFperiod, the shift amount and the liquid flow rate as standard processingparameters (n steps: n≧1) during nozzle contact (i.e., when the nozzlesare in contact with the workpiece). The liquid flow rate changing means32 changes the liquid flow rate (liquid flow rate parameter) sent by theprocessing parameter storage means 5 based on the liquid flow ratedetermined by the liquid flow rate determining means 30, and the changedliquid flow rate is output to the controller 7 and displayed on thescreen (not shown) of an output/display means 6.

[0042] The processing operation of the first processing step will now bedescribed with reference to FIG. 5. The material quality, platethickness, wire diameter, upper nozzle height, lower nozzle height andthe like are input to the liquid flow rate determining means 30 via theinput means 1 (ST 2-1). The standard processing parameters determinedbased on the material quality, plate thickness, wire diameter and thelike where the nozzles are in contact with the workpiece are storedbeforehand in the processing parameter storage means 5, and thesestandard processing parameters are sent to the liquid flow rate changingmeans 12 (ST 2-2). When the material quality, plate thickness, wirediameter, upper nozzle height, lower nozzle height and the like areinput using the input means 1, the liquid flow rate determining means 30determines the liquid flow rate based on the liquid flow rate from theliquid flow rate database 31 (ST 2-3). For example, where the platethickness is ‘10’, the upper nozzle separation amount is ‘20’ and thelower nozzle separation amount is ‘0’, the liquid flow rate is ‘0.5’according to No. 2 in FIG. 6, and the liquid flow rate is determined as50% of the standard first-step amount by the liquid flow ratedetermining means 30. The ‘50%’ information is sent by the liquid flowrate determining means 30 to the liquid flow rate changing means 32.Based on the liquid flow rate sent by the processing parameter storagemeans 5, the liquid flow rate changing means 32 changes the liquid flowrate for the standard first-step processing (the liquid flow rateparameter) (ST 2-4). The changed first-step liquid flow rate is sent tothe controller 33 together with the unchanged processing parameters forthe second and subsequent processing steps, and is displayed on thescreen (not shown) of the output/display means 6 (ST 2-5). Thecontroller 33 performs first-step processing of the workpiece inaccordance with the changed liquid flow rate. During the second andsubsequent processing steps, because one side of the wire is open and isnot affected by the liquid flow rate, processing takes place without achange in the liquid flow rate.

[0043] By adjusting the liquid flow rate, the processing liquid flowssmoothly and wire breakage is prevented. For example, it is known thatwhere the upper nozzle is separated from the workpiece, wire breakage isless likely if the upper nozzle liquid amount is about half the normalvalue. According to this Embodiment 2, because the processing liquidamount is controlled in accordance with the nozzle separation amounts,wire breakage can be prevented.

[0044] The liquid flow rate has been described as being stored in theliquid flow rate database 31, but it is also acceptable if it is derivedthrough an approximate expression for a liquid flow rate sought from thenozzle heights and the plate thickness.

[0045] Furthermore, while standard processing parameters have beendescribed as being stored beforehand in the processing parameter storagemeans 5, it is acceptable if the standard processing parameters aredetermined by different means, such as through user input.

[0046] Embodiment 3

[0047]FIG. 7 is a block diagram showing Embodiment 3 of the presentinvention, and FIG. 8 is a flow chart showing the operation thereof. InFIG. 7, 1 is the same input means, and is normally a keyboard as inEmbodiment 1. 50 is tilt correction value determining means, and 51 is atilt correction value database. As shown in FIG. 9,accuracy-compensating wire tilt correction values corresponding tovarious combinations of workpiece plate thickness, upper nozzle heightand lower nozzle height are stored as wire tilt correction values forall processing steps in normal standard processing. The tilt correctionvalue determining means 50 determines the wire tilt correction valuebased on the data read out from the tilt correction value database 51.The tilt correction value data determined by the tilt correction valuedetermining means 50 is sent to a multi-step tilt correction valuechanging means 52. 53 is a multi-step processing parameter storagemeans, which stores such parameters as the charging voltage, the ONperiod, the OFF period, the shift amount and the tilt of the wire asstandard processing parameters (n steps: n≧1) during nozzle contact(i.e., when the nozzles are in contact with the workpiece). Themulti-step tilt correction value changing means 52 changes theprocessing parameter (wire tilt parameter) sent from the multi-stepprocessing parameter storage means 53 based on the tilt correction valuedetermined by the tilt correction value determining means 50, outputs itto the controller 54, and displays the tilt correction value on thescreen (not shown) of an output/display means 6.

[0048] The operation of Embodiment 3 will now be described withreference to FIG. 8. The material quality, plate thickness, wirediameter, upper nozzle height, lower nozzle height and the like areinput via the input means 1 (ST 3-1). The standard processing parametersdetermined based on the material quality, plate thickness, wire diameterand the like where the nozzles are in contact with the workpiece arestored beforehand in the multi-step processing parameter storage means53, and these standard processing parameters are sent to the multi-steptilt correction value changing means 52 (ST 3-2). When the materialquality, plate thickness, wire diameter, upper nozzle height, lowernozzle height and the like are input using the input means 1, the tiltcorrection value determining means 50 determines the tilt correctionvalue based on the tilt correction value sent from the tilt correctionvalue database 51 (ST 3-3). For example, where the plate thickness is‘10’, the upper nozzle separation amount is ‘20’ and the lower nozzleseparation amount is ‘0’, the tilt correction value is ‘5’ according toNo. 2 in FIG. 9, and this ‘5’ information is sent by the tilt correctionvalue determining means 50 to the multi-step tilt correction valuechanging means 52. The multi-step tilt correction value changing means52 changes the processing parameter, i.e., the tilt (tilt parameter) forthe first through n^(th) steps of standard processing using the tiltcorrection value 5 (ST 3-4). The changed processing parameters for thefirst through n^(th) steps are sent to the controller 54, and aredisplayed on the screen (not shown) of an output/display means 6 (ST3-5). The controller 54 performs first-step through n^(th)-stepprocessing of the workpiece with the wire tilted, in accordance with theprocessing parameters.

[0049]FIG. 10 is an image drawing showing situations in which one of thenozzles is separated from the workpiece. Part (C) of the drawing showsthe case where the upper nozzle 70 and the lower nozzle 71 are incontact with the workpiece 72, while the solid lines in parts (A) and(B) show the case in which the upper nozzle 70 is separated from theworkpiece 72, the wire 73 warps as a result, causing a tapered surface Tto be formed in the workpiece 72 due to discharge repulsion force orelectrostatic force. Accordingly, in the case shown in part (B) of thedrawing, for example, by moving the upper nozzle 70 outward in thedirection of the arrow and tilting the wire 73 by the angle θcorresponding to the tilt correction value of the wire 73, as shown bythe dotted line, the surface of the workpiece can be finished viaprocessing into the vertical surface P. While in Embodiment 3, the wiretilt amount for all processing steps is corrected using the same tiltcorrection value as that saved in the tilt correction value database 51,but it is also acceptable if, for example, correction is performed foronly the n^(th) step, or if a separate tilt correction value is used forthe first step, the second step, etc., up to the n^(th) step.

[0050] Moreover, while the wire tilt correction value has been describedas being stored in the tilt correction value database 51, it may also bederived through an approximate expression for the wire tilt correctionvalue sought from the nozzle heights and the plate thickness.

[0051] Furthermore, while in Embodiment 3 the wire tilt correction valuehas been described as included in the processing parameters, it is alsoacceptable if the wire tilt correction value is stored in a differentform from the processing parameters so long as the wire tilt can becorrected during processing.

[0052] In Embodiments 1 and 2 described above, the processing parametersand liquid flow rate are adjusted so as to prevent breakage of the wireduring the first processing step, but in Embodiment 3, the surfaceprecision and configuration accuracy of the processed surface can beimproved.

[0053] Embodiment 4

[0054]FIG. 11 is a block diagram showing Embodiment 4 of the presentinvention, and FIG. 12 is a flow chart showing the operation thereof. InFIG. 11, 1 is input means, and is normally a keyboard as inEmbodiment 1. 81 is shift amount correction value determining means, and82 is a shift amount correction value database. As shown in FIG. 13,this database stores wire shift amount correction values for theaccuracy-compensating second processing step corresponding to variouscombinations of workpiece plate thickness, upper nozzle height and lowernozzle height as correction values for the shift amount, which is one ofthe above normal standard processing parameters for the secondprocessing step. The shift amount correction value determining means 81determines the shift amount correction value based on the data read outfrom the shift amount correction value database 82. The shift amountcorrection value data determined by the shift amount correction valuedetermining means 81 is sent to the multi-step shift amount correctionvalue changing means 83. 84 is a multi-step processing parameter storagemeans, which stores such parameters as the charging voltage, the ONperiod, the OFF period, and the shift amount as standard processingparameters (n steps: n≧1) during nozzle contact (i.e., when the nozzlesare in contact with the workpiece). The multi-step shift amountcorrection value changing means 83 changes the shift amount parametercorrection value for the second processing step sent from the multi-stepprocessing parameter storage means 84 based on the shift amountcorrection value determined by the shift amount correction valuedetermining means 81, outputs it to the controller 85, and displays theshift amount correction value on the screen (not shown) of anoutput/display means 6.

[0055] The operation of Embodiment 4 will now be described withreference to FIG. 12. The material quality, plate thickness, wirediameter, upper nozzle height, lower nozzle height and the like areinput via the input means 1 (ST 4-1). The standard processing parametersdetermined based on the material quality, plate thickness, wire diameterand the like where the nozzles are in contact with the workpiece arestored beforehand in the multi-step processing parameter storage means84, and these standard processing parameters are sent to the multi-stepshift amount changing means 83 (ST 4-2). When the material quality,plate thickness, wire diameter, upper nozzle height, lower nozzle heightand the like are input using the input means 1, the multi-step shiftamount determining means 81 determines the shift amount correction valuebased on the shift amount correction value sent from the shift amountcorrection value database 82. For example, where the plate thickness is‘10’, the upper nozzle separation amount is ‘20’ and the lower nozzleseparation amount is ‘0’, the shift amount correction value is ‘10’according to No. 2 in FIG. 13, and the shift amount correction value forthe second processing step of standard processing is determined to be‘10’ (ST 4-3). This ‘10’ information is sent from the shift amountcorrection value determining means 81 to the multi-step shift amountcorrection value changing means 83. The multi-step shift amountcorrection value changing means 83 changes the shift amount, one of theprocessing parameters for the second processing step, using the shiftamount correction value (ST 4-4). The processing parameters for thesecond processing step in which the shift amount has been changed aresent to the controller 85 together with the processing parameters forthe first processing step and the processing parameters for the thirdand subsequent steps, and are output and displayed on the screen (notshown) of the display means 6 (ST 4-5). The controller 85 performsprocessing in accordance with the processing parameters.

[0056]FIG. 14 is an image drawing showing the situation in which theupper nozzle 80 and the lower nozzle 81 are separated from theworkpiece. Where the nozzles are separated, warp is caused in the wire83, and when the second processing step is performed, if the wire 73 isin the position indicated by the solid line, discharge no longer takesplace in the center of the workpiece because the processed surface ofthe workpiece 72 becomes concave. Accordingly, by moving the uppernozzle 80 and the lower nozzle 81 in the direction of the arrow to thepositions indicated by the dotted lines to change the shift amount,processing accuracy can be improved. Here, as shown in FIG. 14, theshift amount is the distance by which the upper nozzle 80 and the lowernozzle 81 are shifted by the same distance (from the positions of thewire and nozzles indicated by the solid lines to the positions indicatedby the dotted lines).

[0057] While the shift amount correction value for the second processingstep is held in the database in Embodiment 4, it is also acceptable ifcorrection is performed only for a different processing step, or if aseparate correction value is held for each individual processing step,such as for the first, second, and nth processing step.

[0058] It is furthermore acceptable in Embodiment 4 if other processingparameters that affect the shift amount are changed. For example, theshift amount may be changed if the ON period, processing conveyancespeed, discharge voltage or the like is changed.

[0059] Embodiment 5

[0060]FIG. 15 is a block diagram showing Embodiment 5 of the presentinvention, and FIG. 16 is a flow chart showing the operation thereof. InFIG. 15, 1 is input means, and is normally a keyboard as inEmbodiment 1. 100 is nozzle height detection means that automaticallyseeks the nozzle heights, 101 is a processing speed database that storesthe relationship between the processing speed and the nozzle separationamounts, and 81 is shift amount correction value determining means. 82is a shift amount correction value database, which stores, as shown inFIG. 17, shift amount correction values for the accuracy-compensatingsecond processing step corresponding to various combinations ofworkpiece plate thickness, upper nozzle height and lower nozzle heightas shift amount correction values for the shift amount, which is one ofthe above normal standard processing parameters for the secondprocessing step. The shift amount correction value determining means 81determines the shift amount correction value based on the data read outfrom the shift amount correction value database 82. The shift amountcorrection value data determined by the shift amount correction valuedetermining means 81 is sent to the multi-step shift amount correctionvalue changing means 83. 84 is a multi-step processing parameter storagemeans, which stores such parameters as the charging voltage, the ONperiod, the OFF period, the shift amount and the like as standardprocessing parameters (n steps: n≧1) during nozzle contact (i.e., whenthe nozzles are in contact with the workpiece). The multi-step shiftamount correction value changing means 83 changes the shift amountcorrection value for the second processing step sent from the multi-stepprocessing parameter storage means 84 based on the shift amountcorrection value determined by the shift amount correction valuedetermining means 81, outputs it to the controller 85, and displays theshift amount correction value on the screen (not shown) of anoutput/display means 6.

[0061] The operation of Embodiment 5 will now be described withreference to FIG. 16. The material quality, plate thickness, wirediameter, and the like are input via the input means 1 (ST 5-1). Thestandard processing parameters determined based on the material quality,plate thickness, wire diameter and the like where the nozzles are incontact with the workpiece are stored beforehand in the multi-stepprocessing parameter storage means 84, and these standard processingparameters are sent to the multi-step shift amount changing means 83.Processing is then begun (ST 5-2). During the first processing step, thenozzle height detection means 100 detects the processing speed andextracts the nozzle heights from the processing speed database 101 shownin FIG. 15 (ST 5-4), and the nozzle heights are displayed on the screen(not shown) of the display means 6, as shown in part (C) of FIG. 18 (ST5-5). Here, FIG. 18 shows a display screen, on which are displayed theupper nozzle 70, the lower nozzle 71, the workpiece 72 and spaces 75 and76 in which are input the heights of the upper nozzle and the lowernozzle. When the value ‘20’ is displayed in the space 75, as shown inpart (C), this value ‘20’ is converted to coordinate data on the displayscreen, and the upper nozzle 70 is displayed at a position where theupper nozzle height is 20 mm. It is known that when the nozzles areseparated from the workpiece, because the amplitude of the wire'soscillation becomes large, the actual processing amount increases, andthe processing speed decreases. According to No. 2 of FIG. 17, if theprocessing speed is ‘5’, the upper nozzle height becomes ‘20’ and thelower nozzle height becomes ‘0’. When the material quality, platethickness and wire diameter are input using the input means 1, and theupper nozzle height and lower nozzle height and the like are input fromthe nozzle height detecting means 100, the shift amount correction valuedetermining means 81 determines the shift amount correction value basedon the shift amount correction values in the shift amount correctionvalue database 82 (ST 5-6). For example, where the plate thickness is‘10’, the upper nozzle separation amount is ‘20’ and the lower nozzleseparation amount is ‘0’, the shift amount correction value is ‘10’according to No. 2 in FIG. 13, and the shift amount correction value forthe second processing step of standard processing is determined to be‘10’. This ‘10’ information is sent from the shift amount correctionvalue determining means 81 to the multi-step shift amount correctionvalue changing means 83. The multi-step shift amount correction valuechanging means 83 changes the shift amount, one of the processingparameters for the second processing step of standard processing, usingthe shift amount correction value (ST 5-7). The processing parametersfor the second step in which the shift amount has been changed are sentto the controller 85 together with the processing parameters for thefirst processing step and the processing parameters for the third andsubsequent steps, and are displayed on the screen (not shown) of theoutput/display means 6 (ST 5-8). The controller 85 performs processingin accordance with the processing parameters.

[0062] While the detected nozzle heights are displayed on the displaymeans in Embodiment 5, it is also acceptable if such display isperformed when the user inputs the nozzle heights in Embodiments 1-4. Inthat case, where the user inputs ‘20’ for the nozzle height, as shown inpart (B) of FIG. 18, when the initial state shown in part (A) is beingdisplayed, the value ‘20’ is converted to coordinate data on the displayscreen, such that a graphic image in which the upper nozzle has moved toa position 20 mm higher is displayed based on the converted values, asshown in part (C).

[0063] In each of the embodiments described above, input is performed bythe user via a keyboard, but it is acceptable if different input meansis used, or if values are input from an external system or the like thatautomatically measures nozzle heights.

[0064] In Embodiment 5, because the processing state is detected as theprocessing speed, correction in accordance with the nozzle heights isautomatically performed even if data such as nozzle heights is not inputby the user, enabling surface precision to be improved.

[0065] Although in each of the above-described embodiments theconstituent elements have been described as provided within thewire-electrical discharge machine, they may be provided in a CAD/CAMsystem separate from the wire-electrical discharge machine, for example.Such a situation is also included in the scope of the present invention,with the understanding that the wire-electrical discharge machineencompasses the separate CAD/CAM system.

[0066] Industrial Applicability

[0067] Because the present invention prevents wire breakage in awire-electrical discharge machine, and increases the surface precisionand configuration accuracy of the processed surface, it can beadvantageously used in wire-electrical discharge machining.

1. A wire-electrical discharge machine that infuses a processing liquidin a gap between a wire and a workpiece and processes the workpieceusing predetermined processing parameters, said wire-electricaldischarge machine comprising: processing parameter storage means thatstores processing parameters; means that stores a relationship between anozzle height and an amount of processing energy; processing energydetermining means that determines the amount of processing energy duringrough processing based on such relationship; and processing parameterchanging means that changes the processing parameters based on theamount of processing energy, whereby the workpiece is processed usingthe changed processing parameters.
 2. A wire-electrical dischargemachine that infuses a processing liquid in a gap between a wire and aworkpiece and processes the workpiece using predetermined processingparameters, said wire-electrical discharge machine comprising:processing parameter storage means that stores standard processingparameters; means that stores a relationship between a nozzle height andan amount of liquid flow; means that determines the amount of liquidflow during rough processing based on such relationship; and liquid flowrate changing means that changes a liquid flow rate parameter among theprocessing parameters, whereby the workpiece is processed using thechanged processing parameters.
 3. A wire-electrical discharge machinethat infuses a processing liquid in a gap between a wire and a workpieceand processes the workpiece using predetermined processing parameters,said wire-electrical discharge machine comprising: processing parameterstorage means that stores standard processing parameters; means thatstores a relationship between a nozzle height and an amount of wiretilt; tilt correction value determining means that determines the amountof wire tilt during processing based on such relationship; and tiltcorrection value changing means that changes a tilt correction valueparameter among the processing parameters, whereby the workpiece isprocessed using the changed processing parameters.
 4. A wire-electricaldischarge machine that infuses a processing liquid in a gap between awire and a workpiece and processes the workpiece using predeterminedprocessing parameters, said wire-electrical discharge machinecomprising: processing parameter storage means that stores standardprocessing parameters; means that stores a relationship between a nozzleheight and an amount of wire shift; shift amount correction valuedetermining means that determines the amount of wire shift duringprocessing based on such relationship; and shift amount changing meansthat changes a wire shift amount parameter among the processingparameters, whereby the workpiece is processed using the changedprocessing parameters.
 5. A wire-electrical discharge machine thatinfuses a processing liquid in a gap between a wire and a workpiece andprocesses the workpiece using predetermined processing parameters, saidwire-electrical discharge machine comprising: processing parameterstorage means that stores standard processing parameters; nozzledistance detection means that detects a processing state in a firstprocessing step and detects a nozzle distance from the detectedprocessing state; and processing parameter determining means thatdetermines the processing parameters for subsequent processing stepsbased on the detected nozzle distance, whereby the workpiece isprocessed using the determined processing parameters.
 6. Thewire-electrical discharge machine according to claim 5, wherein theprocessing state to be detected is a processing speed.
 7. Thewire-electrical discharge machine according to claim 5, furthercomprising means for displaying a state of separation of a wire nozzlein a graphical fashion.